Britain's water vole population has been decimated in recent years, but one man is on a mission to bring it back. Steve Farrar reports

The boy who spent hours nosing around the countryside of northeast Essex came to regard the wild animals that shared his playground as friends - particularly the water voles, the rotund riverside rodents that provided the inspiration for Ratty, hero of The Wind in the Willows .

Rob Strachan recalls his many encounters with the denizens of field, creek and mudflat with affection. Coming face to face with the characters of a favourite children's novel helped foster an obsession with nature at an early age. While his teenage friends spent Friday nights at the local disco, Strachan preferred the natural history society. Unsurprisingly, he went on to become an ecologist and is now an authority on many of the species of mammal he first met as a child.

In 1989, Strachan got the chance to reacquaint himself with his old friends. Anecdotal evidence was mounting that the water vole population was falling. Strachan spent the next couple of years touring Britain in a camper van, seeking evidence of the animals' presence. What he found - or rather did not find - along his travels disturbed him. The water vole was absent from 70 per cent of sites it had once frequented, including those in northeast Essex Strachan knew so well.

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A second survey, in 1995, showed numbers had fallen by another 70 per cent, and a third one confirmed a further decline. Strachan, by now a respected Oxford University scientist, calculated that Britain's water vole population had crashed from 7 million in 1990 to 800,000 by 1998. "They were abundant in the 1960s and 1970s, but if we continue with this rate of decline, the water vole will almost certainly be extinct within the next ten years," he says.

Strachan set himself the task of helping save Ratty. In a pioneering experiment just a few miles from Westminster, 182 water voles were released at the Wetland Centre, Barnes. This remarkable site, close to the Thames in west London, was until recently dominated by four vast Victorian reservoirs. In their place is a network of ponds and channels that are home to thriving wildlife communities.

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It is ideal for water voles - plenty of reed, rushes and sedges to eat, no predators and little threat of sudden floods. Most of these animals are captive-bred, the rest relocated from sites under threat. With microchips and radio tags, the water voles have been monitored and tracked. Researchers have gained insights into their behaviour, such as the four-hour timetable that dominates their lives in a pattern of foraging, nest maintenance and sleep.

In the wetland centre's carefully controlled habitat, reintroduction strategies are being perfected. It seems that the animals thrive best when released in mating pairs at 100m intervals. Most stay close to their release site - though one trekked almost 1km in its first three days. They build their nests within a self-organised network of contiguous territories. Strachan's reintroduction techniques appear to work.

"We can successfully establish them by mimicking natural conditions," he says. Fortunately, the animals breed fast. A pair can have 30 offspring by the end of a single year. Most of the animals survived the winter, new animals have been absorbed into the population and many pairs have already started mating.

But outside Barnes, it is a different story. There has been widespread destruction of the water vole's habitat through a combination of intensive agriculture and urban encroachment. American mink have preyed on the voles to devastating effect.

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Strachan knows it will take more than effective release protocols to reintroduce the species. Three years ago, he began recruiting farmers working the coastal plain south of Chichester, an area where 95 per cent of the water voles have disappeared.

This group of 28 farmers is being encouraged through environmental stewardship incentives to manage the land in ways that should allow the animal to recolonise lost reed beds and re-establish contact with neighbouring populations. Ultimately, the results of this work could inform a national strategy to restore the water voles' habitat.

Combined with the lessons of the Barnes study and perhaps new forms of mink control, Strachan is optimistic that the species could make a full comeback within a decade. "Consider life without Ratty. We want to make sure the water vole is there for future generations to enjoy," he says.

When the centenary of The Wind in the Willows is marked in six years, Strachan hopes its diminutive hero will be making personal appearances up and down the country.

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